A major direction in our research program has been the study of the effects of C-reactive protein (CRP) upon platelet function where we have found this acute phase reactant to modulate platelet aggregation and release reactions; we have now begun to investigate the role that CRP might play in altering platelet arachidonate metabolism with particular attention being paid to events encompassing the enzymatic cleavage of arachidonate and its subsequent entrance into the prostaglandin generating pathway. We have also begun studies to elucidate and characterize the binding reaction between CRP and the platelet; to define the capacity of complexed CRP to modulate platelet activity and to assess what molecules present in normal or acute phase plasma can serve as binding specificities for CRP; and to define the possible platelet regulatory function inherent in other acute phase reactants that are either structurally similar to CRP or whose kinetics of production are like that of CRP. Thus, our major objectives have become to define and characterize the effects of CRP upon platelet arachidonate metabolism, the binding reaction between CRP and the platelet, the platelet modulatory activity of CRP in complexed form, and the contribution of other acute phase reactants alone or in combination with CRP upon the reactivity of the platelet. It is hoped that a study of this nature will contribute to a better understanding of the platelet regulatory effects of CRP in particular, and the acute phase in general, and gain sufficient insight into these mechanisms to allow for their favorable external manipulation.